Safety device for elevators



Aug. 18, 1931. J. DUNLOP SAFETY DEVICE FOR ELEVATORS Filed Feb. 6. 1929 INVENTOR James Dunlop ATTORNEY Patented Aug. 18, 1931 warren STATES PATENT OFFICE? JAMES DUNLOP, or PARK- RIDGE, ILLINOIS, nssxenon, BY innsnn ASSIGNMENTS, "r0

WESTINGHOUSE ELECTRIC ELEVATOR COMPANY, A CORPORATION OF ILLINOIS SAFETY DEVICE FOR ELEVATORS Application filed February 6, 1929. Serial No.,337,950.

My invention relates to safety devices for elevators and more particularly to devices for safely stopping and holding an elevator car or its counterweights in the event that either should start to fall or run away, downwardly.

The object of the invention, generally stated, is the provision of a safety device that shall be simple and efficient in, operation, and adapted forready and economical manufacture and installation.

' A more specific object of my invention is to provide a safety device for an elevator in which the gripping jaws will be applied quickly to the guide rails when the downward s eed of the elevator car or the counterweig ts "on which it is mounted exceeds a predetermined limit.

Another object of my invention is to provide for operating the gripping jaws of a safety device at a rapid rate of speed during the first part of their movement and at a lower rate of speed during the latter part of their movement, in gripping the guide rails to stop the car or the counterweights.

A further object of myinvention is to provide for'cushioning the action of the safety device on the car or its counterweights in bringing them to a stop.

It is also an object of my invention to provide for bringing the car and its counterweights slowly to a stop when the safety device thereon is operated by the falling or running away of the car.

Other objects will, in part, be obvious and will, in part, appear hereinafter.

For an illustration of one of the many forms my invention may take, reference may be had to the accompanying drawings, in which,

Figure 1 represents an elevator provided with a device constructed in accordance with my invention for bringing the car to a stop when it starts to fall or run away downwardly.

Fig. 2 is a top plan view, partially in section, of the safety device embodied in the structure illustrated in Fig. 1, showing the manner in which the operating drum and While my invention may be applied to any up and down movable body connected with an elevator such as the car or its counterweights, the drawings, for the sake of simplicity, illustrate it as applied to an elevator car G that is suitably suspended by a plurality of cables Ca between a pair of guide rails 11 and 12. v

As shown, the car G is provided with a safety grip device 13, a speed governor controlled rope 14, for setting the safety device into operation when the car falls or starts to run away downwardly, and a cushioning or bufier device 15 for easing the shock upon the car when it is stopped quickly by the safety grip device.

The safety device 13 is movably mounted in 'a frame-work 16 that is secured to the bottom of the car, and comprises a frame 17 and two pairs of jaws 18 and 19 that are pivotally mounted on the outer ends of the frame in position to grip the guide rails 11 and 12.

The means for moving the gripping jaws 18 and 19 into and out of engagement with the guide rails 11 and 12 comprises a safety drum 20 disposed between a pair of cross members 21 and 22 on the safety device frame 17 The drum 20 is mounted on a travelling nut 23 that is rotatably andslidably journalled in the cross members 21 and 22. A key 24 is disposed in a keyway in the drum 20 and the travelling nut 23 to cause rotation of the nut when the drum is rotated. p

A cooperating travelling nut 27 is rotatably and slidably j ournalled in an additional 4 pair of'cross members 25 and 26 in alignment with the travelling nut 23. The cooperating travelling nut 27 is also connected to and driven by the safety drum 20 through a gear wheel 30, a pinion 31, a shaft 32, a pinion 33 and a gear wheel 34.

The outer ends of the travelling nuts 23 and 27 are provided with right and left-hand screw-threaded central apertures and 36 for receiving the inner screw-threaded ends of a pair of aligned push rods 37 and 38, that are mounted in bearing plates 39 and 40 which are secured to the cross members 21 and 26, respectively.

The push rods 37 and 38 are slidably disposed in the bearing plates 39 and 40, but are prevented from rotating therein by means of a pair of keys 41 and 42. Therefore, when the travelling nuts 23 and 27 are rotated, they Will, because of their screw threaded connection with the push rods 37 and 38, move the push rods outwardly in an axial direction.

Mounted on the outer ends of the push rods 37 and 38 are cam shaped members 43 and 44 that are respectively disposed between a pair of rearwardly extending arms 45 and 46 on the jaws 18 and a pair of rearwardly extending arms 47 and 48 on the jaws 19, for moving the jaws into engagement with the guide rails 11 and 12 when the push rods are. operating outwardly by the operation of the travelling nuts.

A pair of tension springs 49 and 50 are mounted on the rearwardly extending arms 45 and 46 and 47 and 48 of the gripping jaws for the purpose of withdrawing the jaws from the guide rails 11 and 12 when the cam shaped members 43 and 44 are withdrawn from between the rearwardly extending arms.

The means for rotating the safety drum 20 to operate the gripping'jaws when the car starts to fall or run away downwardly comprises a safety rope 55, one end of which is wound around secured to the drum and the other end of which passes over apair of sheaves 56 and 57 on the frame 16 to the governor rope 14, to which it is securely fastened by a clamp 58.

The governor rope 14 is releasably at tached to the car C by means of a suitable yielding connection 60 and passes over a sheave 61 on a centrifugal governor 62 at the top of the hatchway, for the purpose of rotating the governor in accordance with the speed of the up and down movements of the car- The governor 62 may be of any suitable construction such as will, when operated above a predetermined speed, actuate a cam lever 63 to lock the governor rope 14 against further movement. Thus it will be seen that if the car C, while descending, moves the governor rope 14 to operate the centrifugal governor 62 above a predetermined speed, the governor will actuate the cam lever 63 to lock the governor rope against further movement. hen the governor rope 14 is locked against further movement while the car is descending, it will be pulled free from the yielding connection 60 and, as the car continues to descend, will exert such a pull on the safety rope 55 as will cause that rope to be pulled away from the safety drum 20, thereby rotating the safety drum to apply the gripping jaws 18 and 19 to the guide rails 11 and 12 for stopping the car.

As shown, the safety drum 20 is provided with a bevel gear face 59 that may be engaged by any suitable means for rotating the drum to rewind the safety rope 55 thereon and permit the gripping aws to be withdrawn from the guide rails when it is desired to reset the safety device.

In order that the gripping jaws 18 and 19 may be moved into gripping action against the guide rails 11 and 12 as soon as possible after the safety device 13 is tripped and set into operation by the governor rope 14, the cooperating inner ends of the travelling nuts 23 and 27 are provided with cooperating cams 65 and 66 to throw them apart as soon as they start to rotate.

The projecting cam 66 is disposed on the inner end of the travelling nut 27 in such position that it will rest in a notch 67 in the travelling nut 23 when the nuts are not in operation, but will impinge against the cam face 65 when the nuts are rotated by the safety drum 20.

In order to cause the cam 66 to impinge against the cam 65 when the nuts 23 and 27 are rotated, it is necessary to cause the nuts to be rotated. at different relative speeds, and for this purpose the safety drum 20 is keyed fast to the travelling nut 23 while the gear wheels 30 and 34 and the pinions 31 and 33 are constructed of such relative sizes that the travelling nut 27 will rotate faster than the safety drum when the latter is rotated. Therefore, when the safety drum starts to rotate, the cam 66v will move out of the notch 67 against the cam 65and cause the travel-. ling nuts to separate and shove the push rods 37 and 38 apart, thereby quickly bringing the gripping jaws 18 and 19 into engagement with the guide rails 11 and 12 with the initial movement of the car after the governor has been tripped and further movement of the car will tighten the grip of jaws 18 and 19 as push rods, 37 and 38 are moved outwardly by the action of their screw threads.

The inner end of the travelling nut 23 is provided with an aperture 68 in which a rounded projection 69 on the inner end of the cooperating travelling nut 27 is rotatably and slideably disposed, for the purpose of keeping the ends of the travelling nuts correctly aligned and supplying a strong sup port for the cams 65 and 66 when they are forcing the travelling nuts apart.

As shown, a pin 69 is disposed in the wall of the inner part of the nut 23 to engage a slot 70 in the inner end of the nut 27 and force the nuts together so that the cam 66 will be located in the notch 67 when the safety device is reset after being operated."v

It will be understoodby those skilled in the elevator art that application of the safety grip to the rails will cause-the grip device to stop substantially I instantaneously, and suchrapid stop is most uncomfortable to passengers on the car if it does not actually cause them injury, hence I provide acushioning device 15 for lessening the shock to the car when it, is'stopped suddenly by the safety device, which is secured directly to the bottom of the car and is provided with a plunger 73 that extends-downwardly into a liquid containing-cylinder 74 which is secured to the frame 17 of the safety device. The plunger 73 is provided with a central aperture 75 that permits the liquid in the cylinder 74 to? flow into a cylinder 76 when the plunger 73 is forced downwardly into the cylinder 74 by the descent of the car on the safety device after the safety device is tripped and stopped by the governor rope.

Mounted in the cylinder 76 is a pair of pistons 77 and 7 8 that are adapted to be moved outwardly by the liquid forced from the cylinder 74. A pair of auxiliary push rods 79 and 80 are provided for connecting the pistons 77 and 78 to two pairs of auxiliary gripping jaws 81 and 82 on the outer ends of the cushioning device in such manner that the jaws will be moved into gripping engage,- ment with the guide rails 11 and '12 when the pistons are operated by a flow of liquid from the cylinder 74 for the purpose additionally of retarding the descentof the car upon the safety device.

The operation of the apparatus is as follows: Assuming that the elevator car C starts to fall, then the governor rope 14, being attached to the car by the releasable means 60, will be moved over the sheave 61 at such a speed that the centrifugal governor 62 will be operated to trip the cam lever 63 and lock the governor rope against further movement. As the car continues to descend after the gov ernor rope 14 is locked against further movement, the governor rope is pulled free from the releasable connection 60 on the car and thereby exerts a pull upon the safety rope 55. The pull on the safety rope causes it to unwind from and rotate the safety drum 20, thereby effecting rotation of the travelling nuts 23 and 27.

ing the continued rotation of the travelling nuts at different relative speeds will cause them to be forced apart quickly. As the travelling nuts are forced outwardly by the engagement of the cooperating cams and 66, the push rods that are secured to the travellingj nuts will be shoved outwardly and their cam shaped ends 43 and 44 will be respectively forced between the rearwardly extending arms 45 and 46 on the jaws 18, and 47' and'48 on the jaws 19, thereby quickly setting the gripping jaws against the guide rails 11 and 12.

As the safety drum continues to rotate the travelling nuts 23 and 27, the screw-threaded connection between the nuts and the push rods 37 and 38 will cause the latter to continue their outward movement at a rate that will be determined by the pitch of the screwthreaded connections and thereby exert an increasing pressure on the gripping jaws until the safety device is brought to a stop.

Inasmuch as the safety device is slideably secured tothe frame work 16, by meansof a plurality of cleats 83, the car will continue to descend upon the safety device after the safety device is stopped. However, as the car descends upon the stopped safety device, the plunger 73 on the cushioning device 15 will be forced downwardly in the cylinder 74 on the safety device and, by reason of its action upon the fluid in the cylinder, will tend to retard the car and bring it slowly to stop on the safety device.-

As the car continues downwardly toward the stopped safety device, the fluid that escapes from the cylinder 74, through the central aperture 75 in the plunger 73, to the cylinder 76, will force the pistons 77 and-7 8 outwardly, thereby actuating the push rods 7 9 and 80 to move the gripping jaws 81 and 82 into gripping engagement with the guide rails 11 and 12 andadd an additional retarding effect to cause the car to settle down gently upon the safety device and come to a stop safely.

After the fault causing the car to overspeed has been corrected, the safety device may be resetby any suitable means for engaging the bevel gear 59 on the safety drum 20 and rotating the drum in a reverse direction until the safety rope 55 is 'rewound thereon and the parts resume their normal position.

Therefore, itwill be observed that I have provided an improved safety device for an elevator carthat will operate quickly to take up any lost motion in its various parts when actuated by the safety governor and which will at the same time provi'de'for cushioning the stopping of the car so that it will be promptly and safely brought to a standstill.

While I have illustrated and described only one specific embodiment of my invention as applied to an elevator car, I realize that it is susceptible of wide applicatiomand I do not L'Il desire to be limited to the precise construction and use illustrated and described.

I claim as my invention 1. In a safety device for an elevator body, the combination with a plurality of cooperating jaws for gripping cooperating rails to stop the body, a pair of rods for operating the jaws, and a pair of nuts connected with the rods, of means for rotating said nuts at different relative speeds for actuating said rods to operate said jaws, and means operably responsive to the rotation of the nuts at different relative speeds for moving the nuts bodily to cause a rapid initial engagement of the jaws with the rails.

2. In a safety device for an elevatorbody, the combination with a plurality of cooperating jaws for gripping cooperating rails to stop the body, a pair of rods for operating the jaws, and a pairof nuts for operating the rods and provided with cooperating cams, of means for rotating said nuts at different relative speeds, to cause engagement of the cams for moving the nuts bodily and thereby effecting a rapid initial engagement of the jaws With the rails.

3. In a safety device for an elevator body, the combination with a plurality of cooperating jaws for gripping cooperating rails to stop the car, a pair of rods for operating the jaws, and a pair of nuts for operating the rods and provided with a pair of cooperating cams, of means for rotating said nuts at different relative speeds to cause engagement of the cams and thereby force the nuts apart for effecting a rapid initial engagement of the jaws with the rails.

4;. The combination with a safety device for stopping an elevator body, means for suspending the safety device beneath the body to permit relative movement of the car and the safety device and means for operating the car, of a retarding means disposed on the body, pressure-responsive actuator means for said retarding means and fluid pressure generating means operably responsive to operation of the safety device and a ively re po s e to p rati n of h sa y dev ce for gene atinga flu d pr ur to cushion the descent of the body on the safety de ic two pairs of auxilia y gripp g ja disposed on the body for engaging a pair of cooperatingv rails for retarding the descent of the body on the safety device and a fluid operated means associated with each pair of auxiliary gripping jaws and operably rep nsive to t e g nera io o id P ure in said fluid container for operating said auxiliary gripping j aws,

7. The combination with an elevator car and a safety device disposed beneath it for stopping it, of braking devices carried by the car, a fluid-pressure buffer disposed between the car and the safety device for cushioning the stoppingof the car when the safety deic is app i d, fl d-Pre ur PQn$i e a tuator members carried by the car for applying said braking devices, and means for supplying pressure from the fluid-pressure buffer to the pressure-responsive actuator members to actuate the braking devices on the car when the safety device is applied.

In testimony whereof, I have hereunto subscribed rny name this 29thday of January J AM S D N O conduit means for supplying fluid pressure p to said actuator means to apply the retarding means to retard the descentof the body on the safety device. 7

- 5. The combination with a safety device for stopping an elevator body, means for suspending the safety device beneath the body to permit relative movement of the car and the safety device and means for operating the safety device, of a plurality of auxiliary gripping jaws disposed on the body for engaging a pair of cooperating rails, fluid pressure operated actuator means for applying the auxiliary gripping jaws to the rails for retarding the descent of the body on the safety device, fluid-pressure-generating means responsive to operation of the safety device, and-conduit means for transmitting Y 

